Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, touch sensor panels, joysticks, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface. The touch sensor panel can be positioned in front of a display screen so that the touch-sensitive surface covers the viewable area of the display screen. Touch screens can allow a user to make selections and move a cursor by simply touching the display screen via a finger or stylus. In general, the touch screen can recognize the touch and position of the touch on the display screen, and the computing system can interpret the touch and thereafter perform an action based on the touch event.
Touch sensor panels can be implemented as an array of pixels formed by multiple drive lines (e.g. rows) crossing over multiple sense lines (e.g. columns), where the drive and sense lines are separated by a dielectric material. An example of such a touch sensor panel is described in Applicant's co-pending U.S. application Ser. No. 11/650,049 entitled “Double-Sided Touch Sensitive Panel and Flex Circuit Bonding,” (U.S. Patent Application Publication No. 2008/0158181), filed on Jan. 3, 2007, the contents of which are incorporated by reference herein.
However, fingers and palms inadvertently in close proximity with a touch sensor panel can cause unintended gestures to be recognized and processed. These inadvertent touches can often occur when the touch sensor panel is separate from but adjacent to other input devices being used, such as a conventional keyboard or mechanical buttons or bars. Additionally, when the touch sensor panel itself is being used, fingers such as those used for stabilization of the hand (but not part of the gesture) or holding the device can accidentally touch the edges of the panel and be detected.